1. Field of the Invention
The present invention relates generally to a swash plate type compressor used for the air conditioner of an automobile, and more particularly to a compressor with a pulsation pressure reducing structure, which is capable of reducing the noise of the pulsation pressure of refrigerant discharge in the process of refrigerant being compressed and discharged, thereby allowing the compressor to have a low operating noise.
2. Background of the Related Art
Generally, a compressor constituting a principal element of the cooling system of the air conditioner of an automobile is an apparatus that selectively receives power from an engine through a pulley by the intermittent action of an electromagnetic clutch, compresses vapor refrigerants having exchanged heat in an evaporator into high-temperature and high-pressure refrigerant easy to be liquefied, and discharges the resulting refrigerant to a condenser.
Such a compressor may be generally classified into a reciprocating type or rotary type according to its refrigerant compressing manner and refrigerant compressing structure.
The swash plate type compressor belonging to the reciprocating compressor is constructed to suck, compress and discharge low pressure refrigerant having been evaporated in an evaporator, in such a manner that a disc-shaped swash plate slantly mounted around a driving shaft to which the power of the engine is applied is rotated by means of the driving shaft and a plurality of pistons coupled by means of a shoe with the periphery of the swash plate are rectilinearly reciprocated through a plurality of bores formed on a cylinder. According to piston pressurizing manners, such the swash plate compressor may be classified into a single head piston type in which pressurizing force is applied to only the one face of the piston or duplex head piston type in pressurizing force is applied to the both faces of the piston.
The present invention relates to the single head piston type compressor, and more particularly to a variable displacement swash plate type compressor in which the inclination angle of its swash plate is varied, thereby making it possible to vary the amount of the reciprocating movement of the piston, such that the amount of compression of the refrigerants can be adjusted in accordance with thermal load.
The variable displacement swash plate type compressor has the following advantages when compared with a fixed displacement swash plate type compressor: that is, the variable displacement swash plate type compressor has a reduced number of parts, so it is lightweight and its refrigerant compressing capacity can be controlled depending on thermal load, thereby effectively adjusting a room temperature and improving the driving performance of an automobile.
FIG. 5 illustrates an example of a conventional variable displacement swash plate type compressor, wherein the internal construction thereof is shown.
As depicted in the drawing, the conventional variable displacement swash plate type compressor includes: a cylinder block 101 provided with a plurality of cylinder bores 103 in a longitudinal direction through the interior thereof; a front housing 111 positioned in front of the cylinder block 101 to define a crank chamber 113 in the interior thereof; a rear housing 121 coupled to the rear side of the cylinder block 101 to define a suction chamber 123 and a discharge chamber 125 in the interior thereof; a plurality of pistons 131 adapted to be inserted into each of the plurality of cylinder bores 103 of the cylinder block 101 to be moved forward and rearward and provided on their rear ends with a plurality of bridges 133; a driving shaft 141 adapted to be inserted into the center of the cylinder block 101 through the front housing 111 and thus rotatably supported by the front housing 111 and the cylinder block 101; a lug plate 151 adapted to be fixedly attached to the driving shaft 141 in the interior of the crank chamber 113 and thereby rotated with the driving shaft 114; a swash plate 161 adapted to be fitted slantly to the driving shaft 141 in the crank chamber 113 in such a manner as to be adjusted in the inclination angle thereof, fitted through a shoe to a swash plate receiving groove of the bridge 133 on the rear end of each piston 131 on the outer periphery thereof and hinge-coupled rotatably to the lug plate 151 on the one side of the front surface thereof, thereby rotating with the lug plate 151; and a valve plate 173 provided with a plurality of suction holes 175a and a plurality of discharge holes 175b for the plurality of cylinder bores 103 of the cylinder block 101, between the cylinder block 101 and the rear housing 121 and disposed, with a suction reed valve 175 and a discharge reed valve 177 for opening and closing each of the suction holes 175a and discharge holes 175b, between the front and rear sides of the cylinder block 101 and the rear housing 121, such that each bore 103 of the cylinder block 101 can be closed relative to the suction chamber 123 and the discharge chamber 125 of the rear housing 121. A reference numeral 191 denotes a pressure control unit, which compares the pressure in the crank chamber 113 with the pressure in each bore 103 and controls the resulting pressure value, thereby varying the inclination angle of the swash plate 161.
The compressor constructed as described above compresses refrigerant and discharges it to a condenser (not shown) while all the elements of the compressor operate in cooperation with one another.
First, when the driving shaft 141 selectively receives the rotary force of the pulley (not shown), to which the driving force of an engine is transmitted, by the intermittent action of the electromagnetic clutch (not shown) through a disc and hub assembly (not shown) and rotates, the lug plate 151 fixedly attached around the driving shaft 141 rotates together with the driving shaft 141, resulting in the rotation of the swash plate 161 hinge-coupled to the lug plate 151. At this time, the swash plate 161 is swung in an axial direction on the outer periphery thereof due to the inclination angle relative to the driving shaft 141, such that each piston 131 engaged with the outer periphery of the swash plate 161 carries out a rectilinear reciprocating movement in an axial direction in each cylinder bore 103. During this process, positive pressure and negative pressure are alternately produced in each bore 103 so that the refrigerant are sucked, compressed and discharged.
The conventional swash plate type compressor compressing refrigerant through the aforementioned process compresses the refrigerant by the rectilinear reciprocating movement of the pistons performed periodically at predetermined intervals, such that the flow of refrigerant has pulsation pressure having the same period as the refrigerant discharge period of each piston 131 while the refrigerant is discharged from each cylinder bore 103 through the discharge chamber 125 and the discharge hole 129. As a result, the conventional swash plate type compressor is problematic in that a driving noise is caused by the pulsation pressure.
In order to solve the problem of the noise caused by the pulsation pressure, for example, in case of the duplex head piston type compressor where pressure is applied to the both faces of the piston, the pulsation pressure can be somewhat reduced in such a manner that the pulsation pressure of the compressed refrigerant discharged from the front housing is overlapped with the pulsation pressure of the compressed refrigerants discharged from the rear housing. However, in case of the single head piston type compressor where pressure is applied to only the one face of the piston, the single head piston type compressor cannot adopt the pulsation pressure reducing method of the duplex head piston compressor, in which two refrigerant flows discharged from two refrigerant discharge chambers are overlapped with each other, because the single head piston type compressor has only a single refrigerant discharge chamber 125 formed beside one side of the cylinder block, as shown in FIG. 5.
In order to remove the driving noise, there has been used a technique in which the conventional single head piston compressor is provided on one side of the outer circumferential surface of the cylinder block 103 or the rear housing 121 with a muffler 181 having a large volume that communicates with the discharge hole 129 of the rear housing 121 and a discharge pipe passage (not shown) connected to the discharge hole 129.
In this case, however, the provision of the muffler 181 on one side of the outer circumferential surface of the cylinder block 103 or the rear housing 121 causes the overall volume of the compressor to be substantially increased, such that the compressor is not compact. Moreover, the compressed refrigerant is forcibly delivered from the discharge chamber 125 through only the single passage coupled to the one discharge hole 129 and the discharge pipe passage (not shown), so a pulsation pressure reducing effect is not sufficient and, therefore, a driving noise is still great.
An object of the present invention is to provide a compressor with a pulsation pressure reducing structure where the pulsation pressure upon refrigerant discharge necessarily generated during refrigerants are compressed and discharged is reduced, even if it is a swash plate compressor using a single head piston; to provide such a compressor which does not need any increase in volume; and to provide such a compressor which is compact and makes substantially less driving noises.
In order to accomplish the above object, the present invention provides a compressor with a pulsation pressure reducing structure, comprising: a cylinder block provided with a plurality of bores radially arranged to be extended therethrough in forward and backward directions; a front housing positioned in front of the cylinder block to define a crank chamber that communicates with the bores of the cylinder block in the interior thereof; a rear housing coupled to the rear side of the cylinder block by disposing a plurality of suction and discharge reed valves for opening and closing a plurality of suction holes and discharge holes having the same number as that of the bores of the cylinder block on the front and rear sides of a valve plate, between the cylinder block and the rear housing, providing a suction chamber and a discharge chamber that communicate with the plurality of bores through the plurality of suction holes and the plurality of discharge holes in such a manner to be separated from each other, on the rear side of the cylinder block, and providing a suction pipe passage that communicates with the suction chamber and a discharge pipe passage that communicates with the discharge chamber through at least two discharge holes separated from each other relative to the plurality of discharge holes of the valve plate; a driving shaft adapted to be extended through the front housing in such a manner as to be disposed on the center of the crank chamber in a longitudinal direction of the cylinder block and supported by means of the front housing; a lug plate adapted to be fixedly attached around the driving shaft of the crank chamber and rotated by the driving shaft; a swash plate adapted to be slantly fitted around the driving shaft and hingedly attached to the lug plate to be rotated together by the lug plate; and a plurality of pistons adapted to be engaged with the outer periphery of the swash plate to perform reciprocating movement within the bores of the cylinder block by wobbling of an outer periphery of the swash plate in the forward and backward directions according to the rotation of the driving shaft.
The at least two discharge holes connecting the discharge chamber to the discharge pipe passage in the rear housing may be spaced apart from each other so that refrigerant flows, which are discharged from the discharge chamber through the at least two discharge holes to the discharge pipe passage while having a pulsation pressure of the same period, by an interval to allow the refrigerant flows to have a phase difference at a position where the two refrigerant flows meet.
The phase difference between pulsation pressures of two refrigerant flows may be a half of a period of the pulsation pressures.
The suction holes connecting the suction pipe passage to the suction chamber in the rear housing may be at least two in number, and spaced from an inlet of the suction pipe passage by different distances.